Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Currency translation adjustment	$ (80)	$ 51	$ 166	$ 193
Net carrying value of software developed	185	140
Vehicle interest income	13	10	9
Advertising expense	123	112	116
Investments in joint ventures	36	46
Aggregate realized gain from the sale of investments		7
Retained risks of liability to third parties	413	397
Workers compensation liabilities	70	67
Business Acquisition, Transaction Costs	18
Business Combination, Contingent Consideration, Liability	9
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability	13
Business Combination, Contingent Consideration, Liability, Favorable Currency Exchange Rate Movements	4
Gain or loss of currency transactions	$ 11	$ 9	$ 11